This invention is designed to solve not only the problem of preventing contamination caused by disposable syringes if they are reused by the users, since this is a current problem of world interest, this problem is completely solved with the syringes which render themselves unreusable, which are the subject of the aforementioned Patent Application, but this invention also provides the solution to the problem of the possible reuse of syringes by drug addicts, a problem which was not completely solved with the aforementioned syringes which rendered themselves unreusable.
The improvements set forth in this invention make the use of the syringes more effective and easier and prevent their possible reuse, even in a partial manner, as well as preventing the possible reuse of the injection needle. The aforementioned syringes could have their needles reused inasmuch as regular needles were used. For this reason, one of the aspects of this invention is to prevent the possible reuse of the needles.
My U.S. Pat. No. 3,667,657 shows a pre-filled syringe in which a non-retractable knife destroys the syringe on use. There are some injectable solutions which cannot be stored for a given amount of time in containers made of material which can be cut with a blade, such as plastic or similar materials. For this reason there is a necessity for a syringe for these types of solutions which can be filled without the blade cutting the cylinder at the time that the solution is extracted from its container in the process of filling the syringe. My Mexican Pat. No. 107,080 shows attaching a resiliently mounted knife to one of the sides of the flaps of the piston rod. However, in this fashion the resiliently mounted knife does not move radially of the piston rod and does not squarely strike the inner surface of the cylinder of the syringe, resulting in a difficult and imprecise cutting action. It is an object of this aspect of the invention that the cutting blade be operated most efficiently so as to permit cutting of the syringe with the minimum additional force required by the user and with maximum reliability in operation.
In accordance with one aspect of the invention the cutting blade is supported on the piston rod by a resilient mounting so that said knife moves radially of the central axis of the cylinder and thus squarely meets the interior surface of the cylinder of the syringe. The knife cuts a half-groove weakening extending longitudinally of the cylinder of the piston after first passing through a full groove or a deepened groove at one end of the half-groove. In a preferred embodiment of the invention the movement of the knife is controlled by guiding means also affixed to the piston rod, such as a slotted plate, which keeps the knife in a plane passing through the central axis of the cylinder. In this way the position of the knife, which is generally planar, is maintained in a position properly to cut the inner surface of the cylinder. The slotted plate also insures that the knife passes outwardly through the full slot in the cylinder when the piston is brought into its retracted position during the aspiration of the syringe with the injecting fluid.
By placing the compressible cutting blade within a recess in one of the flaps of the plunger of the syringe or in an integral seat in said plunger, one also simplifies the manufacture of the syringe and allows uniform pressure during the cutting.
Manufacture is simplified since the weakening of the outside of the cylinder does not have to be outside of the diametrically opposed point of the stops which function as guides for the flaps of the plunger, but it may coincide with said diametrically opposed point generally the entire length of the cylinder.
One embodiment of the invention consists of a blade supported by a laminated or other type spring located in the stated slot and which allows the placing of the blade inside said stated seat in the flap of the plunger. This model may be used in empty syringes in which the blade, during the filling or aspiration process, which is to say, during the time that the plunger is removed to its outermost position, will not cut the cylinder because the outer edge is rounded and does not cut, but, nevertheless, when the plunger has been removed a certain distance which corresponds to a determined dose, the blade will come out radially of an opening or slot made in the cylinder which coincides with the end of the groove or weakened section on the outside of the cylinder because of the force exerted by the spring to which it is connected. Rather than the opening crossing the entire wall of the cylinder of the syringe, it could be only a small hollow space which does not extend to the outside surface, forming a step at practically the same height as the space of the longitudinally weakened section of the cylinder in order to prevent the user from introducing any device from the outside, pushing in the blade and reusing the syringe. Upon injecting the solution contained in the syringe, the blade will cut the cylinder radially at the weakened section, thus, destroying the syringe and preventing any further use of it.
Another embodiment of the invention, principally for empty syringes, has a small seat, preferably tubular, located transversely to the axis of the plunger and beyond the disk which supports the piston in which is located a blade connected on one extreme end to a spring located inside the aforementioned seat; this blade has the side opposite the pivot rounded and the other side has a cutting edge and which includes guiding means like a cover of the said seat which also includes a slot with dimensions just slightly larger than the width of the blade which gives it a little play, which, when the plunger is extracted, due to the play of the blade, the same will not cut said cylinder since it moves along the inside of the cylinder, making contact with its rounded edge.
If, at any time during the movement of the plunger in filling the syringe, it is desired to inject the solution, due to the play of the blade, the latter will make contact with the inside of the cylinder with the cutting edge, cutting the wall of the cylinder across a weakened section made by a longitudinal slot outside the cylinder, which is to say, that in this model of the invention, the blade will cut provided that the piston moves toward the needle, i.e., that operation which is properly called injection, irrespective of whether or not the blade is at the end of the movement of the plunger or not, or in any position in between.
Of course, at the end of the groove or weakened longitudinal section, there is placed in the same manner a slot which runs all the way across the cylinder and allows for the exit of the blade through said slot to such a position that allows for the most ideal and simple cutting, destroying and rendering of the syringe unusable again.
For the total introduction of the plunger in this embodiment of the invention, without having the blade cut the cylinder; in the manufacture or assembly process of this syringe a thin spacing sheet is placed between the blade and the inside wall of the cylinder, which will be extracted once the plunger reaches the end of its movement in the area of the pivot of the syringe.
Still another purpose of this invention is to provide in an embodiment of same, a needle which will be nonreusable, which is to say, that it will not be adaptable to another type of syringe and which is incorporated in the same molding or manufacturing operation of the cylinder of the syringe at the end corresponding to the pivot, which this embodiment does not have since it is made up by the same needle.
This special needle which cannot be used on another type of syringe could be, on another model of this invention, integrally made with a positioning socket which could be applied to the extreme end of the cylinder of one of the disposable syringes, subject of this invention, including the syringe container which has a breakable end and over the cylinder the socket of the aforementioned integral needle can be placed.
In view of the fact that in most of the foregoing embodiments, drug addicts can refill, even with a small amount of solution, the destroyed syringe due to the small part of the syringe which is not cut and which corresponds to the size of the piston of the plunger, this invention furthermore includes the following aspects that solves this and other problems.
One of the embodiments of this aspect of the invention, has in the forward part of the piston, a needle or pin which coincides with a weakened position or groove made in the forward part of the cylinder without fully puncturing the wall of the same, in which case, when the solution is injected by the user and the piston reaches the end of its movement, the cylinder will be fully punctured in the said weakened section, preventing a possible reuse, however small it might be, of the syringe inasmuch as the syringe will be completely unusable. Of course this kind of destruction could be combined with the cutting blade which is outlined in the above models.
Another embodiment which solves the last problem mentioned above, has in the center and in the forward part of the piston a ribbed and toothed projection, or any other kind of mechanism which would jam when inserted into the needle on the first application of the solution, and it would stick in the ribbed part of the needle with which it would coincide, jamming the plunger with the needle, making any further reuse impossible. This embodiment could also be combined with the cutting blade as in the foregoing aspect and would include a stop near the extreme end of the cylinder of the syringe container in order to prevent destruction of the syringe when being assembled before the first application, preventing the pin and the jamming mechanism from making the syringe unworkable prematurely.
Yet another embodiment of this invention is applicable to the syringe container which is prefilled with an injectable solution and which may be manufactured in glass, in plastic, or in a combination of glass and plastic, for the plunger or the cylinder of the syringe, it would include some ledges serving as stops on the inside of the cylinder produced by simple pressure on the cylinder from the outside which would function as gaskets against a ratchet or stop located in a seat adjacent to the detention disk of the piston.
The mentioned stop would be guided by a slotted cover of the seat and forced by the working of a spring to which it would be hooked, located inside said seat and connected at its extreme end to the bottom of the same, so that, once the solution is injected, the stop which has its extreme end rounded and backside straight in relation to the bottom of the cylinder, would work against the gaskets pressed into the cylinder, preventing the possibility of returning the plunger once it has moved in the operation of injection. All of the aforementioned stops of this invention could be simply pressed into the cylinder in order to produce a raised section inside or stop in the same and which could be done by means of automatic molds, thermic or any other procedure.
These and other objectives to be obtained for the use of this invention will be better understood and appreciated by the reading of the following description which refers to the drawings of the preferred embodiment of the present invention.